Multi-speed transmission

ABSTRACT

A multi-speed transmission for transmitting power between a first shaft and a second shaft which includes a plurality of gear sets, a plurality of connector gears corresponding to the plurality of gear sets and a shifting mechanism. Each gear set includes a first gear rotatably disposed about the first shaft, a uni-directional free wheeling mechanism between the first gear and the first shaft, and a second gear coupled to the second shaft. The uni-directional free wheeling mechanism permits the first gear to freely rotate about the shaft when the first gear rotates in a preselected direction relative to the rotation of the first shaft and locks the first gear to the first shaft at all other times. The first and second gears are spaced apart from one another but may be interconnected by one of the plurality of connector gears. Each connector gear is movable between an engaged position, which mutually engages the first gear and the second gear, and a disengaged position. The shifting mechanism moves each one of the plurality of connector gears between the engaged position and the disengaged position. The shifting mechanism maintains at least one of the plurality of connector gears in the engaged position at all times. Each gear set includes a free-wheeling mechanism that allows two gear sets to be simultaneously engaged during the shifting sequence without a clutch or a neutral position between gear sets.

BACKGROUND OF THE INVENTION

The present invention relates to a multi-speed transmission fortransmitting power between a pair of shafts. In particular, the presentinvention relates to a multi-speed transmission wherein auni-directional free wheeling mechanism is provided between a gear andits shaft so that the gear rotates freely about its shaft when the gearrotates in a preselected direction relative to the rotation of its shaftand so that the gear is locked to its shaft at all other times. As aresult, only one gear set transmits power from an input shaft to anoutput shaft when a plurality of gears of the input shaft areinterconnected to a plurality of gears of the output shaft.

Transmissions are utilized in a wide variety of vehicles and stationaryequipment to transmit power and to change rotational speeds betweeninput and output shafts. Generally, power is supplied to the input shafteither mechanically or non-mechanically. In applications where power ismechanically applied to the input shaft, a clutch mechanism is usuallyrequired to interrupt the transmission of power and to shift gearspeeds.

Bicycles are examples where the power supply is provided to the inputshaft by non-mechanical means. As a result, the rotation of the inputshaft may be easily interrupted without a clutch mechanism. Bicyclestypically include chain derailleur mechanisms for shifting a drive chainfrom one sprocket to an adjacent sprocket to change speed ratios. Mostmulti-speed bicycles have derailleurs and multiple sprockets at both thefront pedal hubs and rear wheel hubs to provide a variety of speedratios. Furthermore, most chain sprocket systems may be shifted underfull power.

However, chain and sprocket systems suffer from several keydisadvantages. The multiple sprockets at both the front pedal hubs andthe rear wheel hubs are interconnected by the drive chain which extendsalong a substantial length of the bicycle. As a result, chain andsprocket systems are difficult to house or enclose. Consequently, thechain and sprockets are susceptible to damaging impacts and are exposedto road elements such as dirt and water. Damaging impacts may cause thederailleur mechanisms or sprockets to become bent or misaligned whichmay impair shifting between sprockets. Moreover, road elements may alsocome in contact with the derailleur, chain or sprocket to hampershifting or even damage the components. As a result, the performance ofchain and sprocket systems becomes impaired unless the chain andsprocket systems are periodically cleaned and adjusted.

In addition, chain and sprocket systems have inherent design limitationswhich limit the effective number of speed ratios which may be provided.As a result, chain and sprocket systems do not provide as many speedratios as indicated by their conventional designations. For example, abicycle having three sprockets at the front pedal hub and sevensprockets at the rear wheel hub is conventionally designated as a "21speed" bicycle. Although the bicycle has 21 sprocket combinations, the"21 speed" bicycle actually provides only 11 speed ratios as illustratedby Table 1. Table 1 shows twenty-one sprocket combinations and theirassociated speed ratios for a typical "21-speed" bicycle. Table 1 alsoshows the percent of change between speed ratios of adjacent sprocketcombinations.

                  TABLE 1                                                         ______________________________________                                        Speed Ratios and Percent of Change of "21-Sprocket Combination"               Chain and Sprocket System                                                     Pedal Hub Sprocket Teeth                                                      48           38            28                                                 Rear         Percent Rear      Percent                                                                             Rear      Percent                        Hub          of      Hub       of    Hub       of                             Teeth Ratio  Change  Teeth                                                                              Ratio                                                                              Change                                                                              Teeth                                                                              Ratio                                                                              Change                         ______________________________________                                        30    3.69                                                                                 15.4                                                             26    3.20                                                                                 13.3                                                             23    2.82           30   2.92                                                             17.6              15.4                                           20    2.40           26   2.53                                                             15.0              13.3                                           17    2.09           23   2.24       30   2.15                                             13.0              17.6            15.4                           15    1.85           20   1.90       26   1.87                                             15.4              15.0            13.3                           13    1.60           17   1.65       23   1.65                                                               13.0            17.6                                                15   1.46       20   1.40                                                               15.4            15.0                                                13   1.27       17   1.22                                                                               13.0                                                                15   1.08                                                                               15.4                                                                13   0.93                                ______________________________________                                    

As shown in bold by Table 1, the speed ratios provided by the second hubsprocket having 38 teeth and the third hub sprocket having 28 teeth areredundant except for the two lower speed ratios of each sprocket.Similarly, an 18 speed system provides only 10 effective ratios, a14-speed system provides only 9 effective ratios and a 12-speed systemprovides only 8 effective ratios.

As further illustrated by Table 1, chain and sprocket systems also failto provide a smooth power curve. The number of teeth in the rear hubsprockets of chain and sprocket systems are typically selected so as toprovide a degree of uniformity in speed ratios when used in conjunctionwith the pedal hub sprockets. However, because the number of teeth andthe size of sprockets used on bicycles is limited, the combinations offront and rear sprocket teeth are also limited. As a result, chain andsprocket systems result in an erratic percent of change between speedratios which results in a poor power curve. A preferred power curve formost bicycle applications would have a lower percent of change betweenlower speed ratios and a higher "overdrive" percent of change betweenhigher speed ratios.

Furthermore, chain and sprocket systems require extensive shifting ofboth the front and rear sprockets. For example, shifting of the frontsprocket may require additional shifting of the rear sprocket by severalranges just to maintain the same speed ratio. In addition, chain andsprocket systems also require shifting twice or "cross-shifting" toreach all speed ratios. As illustrated in Table 1 for the 21-sprocketcombination bicycle, shifting from the highest speed ratio of the pedalhub sprocket with 28 teeth to the next higher speed ratio would requirefirst shifting to the pedal hub sprocket with 38 teeth and then shiftingfrom the rear hub sprocket with 30 teeth to the rear hub sprocket with26 teeth. This extensive shifting is difficult as well as confusing.

In an attempt to protect chain and sprocket systems from road elementssuch as dirt and water, several modifications have been made tomulti-speed bicycle transmissions. For example, Hartman U.S. Pat. No.4,770,433 (Hartman '433) discloses an enclosed multiple speed drive formountain bicycles. Hartman '433 discloses four drive gears rotatablymounted on a drive carrier and three drive gears rotatably mounted on adriven carrier. Each gear is meshed with a corresponding gear on each offour countershafts. Hartman '433 utilizes a first gear selector to locka selected drive gear to the drive gear carrier and a second gearselector to lock a selected driven gear to the driven gear carrier. Theshifting arrangement of Hartman '433 requires that each gear selector bemoved to a neutral position before engaging a successive gear. As aresult, the transmission does not provide continuous power whileshifting. In addition, because two shifting mechanisms are employed,"cross-shifting" is required to reach all possible speed ratios.Furthermore, the selection of speed ratios is also limited because thedistance from the center line of the gear carrier to the center line ofthe countershaft is fixed and the sum of the radii of each gear set mustexactly match this preset distance. The free-wheeling mechanism shown inFIG. 4 of Hartman '433 is external to the transmission and allows therear wheel to continue to rotate if the rider ceases pedalling. Becauseall thirty-five gears of Hartman '433 are meshed and rotatingcontinuously, the transmission of Hartman creates considerable frictionand results in wasted effort on the part of the rider.

Similarly, Bailey U.S. Pat. No. 4,926,714 (Bailey '714) describes anenclosed multi-gear transmission that requires reverse pedalling toshift gears. However, as with Hartman '433, the transmission of Bailey'714 does not allow for shifting under continuous power. Bailey '714discloses gears rotatably positioned about the pedal shaft. Each gearincludes an internal pawl disposed in a pawl slot within a pedal shaftBailey '714 changes or shifts gear speeds by axially positioning asingle pawl selector finger within a channel adjacent the slot withinthe pedal shaft to cause a selected pawl of a selected gear to engagethe selected gear so as to couple the shaft to the selected gear.Movement of the pawl selector finger out from under the selected pawlcauses the selected pawl to retract within the slot and to be completelydisengaged from its corresponding gear. By selectively positioning thepawl selector finger, different pawls may be forced into engagement withtheir respective gears to provide different speed ratios. As the pawlselector finger 108 is axially moved between pawls, power from the pedalshaft is not transmitted to the output shaft via any gears. The shiftingarrangement of Bailey '714 does not provide continuous power whileshifting. Because the individual pawls of each gear are not biased so asto be in constant engagement with each pawl's respective gear, the pawlsof Bailey '714 do not automatically lock the input shaft to the gear inresponse to the relative rotational directions of the pedal shaft andthe gear.

Moreover, because the center line of the gear shafts are a fixeddimension apart, the transmission of Bailey '714 also provides only arestricted number of different gear radii and speed ratios. As inHartman '433, the transmission of Bailey '714 requires that all of thegears mesh with one another and rotate continuously. Consequently, aconsiderable amount of friction and wasted effort results.

SUMMARY OF THE INVENTION

The present invention is an improved multi-speed transmission fortransmitting power between an input shaft and an output shaft. The inputshaft carries a plurality of differently sized gears and the outputshaft carries a plurality of differently sized gears. The output shaftis rotated at a variety of speeds by interconnecting the differentlysized gears of the input shaft and the output shaft. A uni-directionalfree wheeling mechanism is provided between at least one of theplurality of gears and the gear's shaft. The uni-directional freewheeling mechanism permits the gear to freely rotate about the gearshaft when the gear rotates in a preselected direction relative to therotation of the gear's shaft. The uni-directional free wheelingmechanism automatically locks the gear to the gear's shaft at all othertimes. As a result, only one gear set transmits power from the inputshaft to the output shaft when a plurality of gear sets between theinput shaft and the output shaft are interconnected.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a multi-speed transmission with a right casingremoved and shafts shown in section.

FIG. 2 is a sectional view of the multi-speed transmission taken alonglines 2--2 of FIG. 1.

FIG. 3 is a sectional view of uni-directional free wheeling mechanismsand input gears.

FIG. 4 is a side sectional view of the uni-directional free wheelingmechanisms and input gears of FIG. 3 coupled to an input shaft

FIG. 5 is an end view of a yoke of the multi-speed transmission.

FIG. 6 is a side view of yoke springs, yokes and connector gears pivotedabout a pivot rod.

FIG. 7 is a sectional view of the multi-speed transmission taken alonglines 7--7 of FIG. 1.

FIG. 8 is a side sectional view of a selector cam in engagement with ayoke of the multi-speed transmission of FIG. 1.

FIG. 9 is a side view of the selector cam and shifters of themulti-speed transmission of FIG. 1.

FIG. 10 is a side elevational view of a bicycle incorporating analternate embodiment of multi-speed transmission.

FIG. 11 is a horizontal sectional view of the transmission of FIG. 10.

FIG. 12 is an enlarged sectional view of a portion of the transmissionof FIG. 11 illustrating uni-directional free wheeling mechanisms.

FIG. 13 is a side elevational view of a bicycle incorporating analternate embodiment of a multi-speed transmission.

FIG. 14 is a horizontal sectional view of an alternative embodiment ofthe multi-speed transmission of FIG. 13.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is a multi-speed transmission for transmittingpower between input and output shafts. A first one of the shafts carriesa plurality of differently sized gears while a second one of the shaftscarries a gear. The output shaft is rotated at a variety of speeds byinterconnecting the gears of the input and output shaft. A plurality ofuni-directional free wheeling mechanisms are between the first one ofthe shafts and the plurality of differently sized gears. Each one of theplurality of uni-directional free wheeling mechanisms is aligned withand corresponds to one of the plurality of differently sized gears. Eachuni-directional free wheeling mechanism permits its corresponding gearto freely rotate about the first one of the shafts when thecorresponding gear rotates in a preselected direction relative to therotation of the first one of the shafts. Each uni-directional freewheeling mechanism further automatically locks its corresponding gear tothe first one of the shafts at all other times. As a result, only one ofthe plurality of differently sized gears of the first one of the shaftsis interconnected to the gear of the second one of the shafts.

The present invention may be used in a wide variety of vehicles andstationary equipment such as motor vehicles, bicycles, winches andblock/tackle equipment. However, for purposes of illustration, thepresent invention is depicted in FIGS. 1-13 for use on a multi-speedbicycle.

Throughout the specification of the application, various terms are usedsuch as "left", "right", "front", "rear" and the like. These termsdenote directions with respect to the drawings and are not limitationsof orientation of the present invention. Rather, these terms areprovided for clarity in describing the relationship between members ofthe transmission. For example, the terms "left" and "right" are used indescribing relationships between components when viewed from the frontend of the multi-speed bicycle.

I. Overview

FIG. 1 illustrates multi-speed transmission 20 from the left side oftransmission 20 with the left casing 82 (shown in FIG. 2) removed.Transmission 20 generally includes transmission housing 24, input shaft26, uni-directional free wheeling mechanisms 28a-28d (best shown in FIG.2), input gears 30a-30h, output shaft 32, uni-directional free wheelingmechanisms 28e-28h (best shown in FIG. 2), output gears 36a-36h (bestshown in FIG. 2), connector gears 40 and shifting mechanism 42. Whenemployed in a bicycle, housing 24 of transmission 20 is preferablymounted at the conventional location of the pedal shaft of the bicycle.Housing 24 substantially encloses and houses transmission 20 to protectit from damaging impacts and to protect the inner components oftransmission 20 from road elements such as dirt and water. Housing 24further provides an enclosure and supporting structure for supportingand maintaining the alignment and positioning of the inner components oftransmission 20. Housing 24 includes openings through which input shaft26 and output shaft 32 project for coupling with the pedal cranks andthe rear wheel sprocket, respectively.

Input shaft 26 is preferably made from the high strength material, suchas steel, capable of withstanding large amounts of torque. Input shaft26 projects through both sides of housing 24 and is coupled to a sourceof rotational power. When used in conjunction with a bicycle, inputshaft 26 of transmission 20 is coupled to left and right pedal cranks(shown in FIG. 2). Power supplied to input shaft 26 is transmitted tooutput shaft 32 across one of the input gears 30, one of the connectorgears 40 and one of the output gears 36 depending upon the desired speedratio. Input shaft 26 carries uni-directional free wheeling mechanisms28a-28d and an array of input gears 30a-30h.

Each uni-directional free wheeling mechanism 28a-28h preferablycomprises a ratchet-loaded pawl mechanism as is conventionally used inthe rear wheel hub of bicycles to allow the rider to cease pedalling andcoast. Uni-directional free wheeling mechanics 28a-28d are preferablyfixedly coupled to input shaft 26 and are positioned between input shaft26 and input gears 30a-30d, respectively. Each uni-directional freewheeling mechanism 28a-28d permits its respective input gear 30a-30d tofreely rotate about input shaft 26 when its respective input gear 30rotates in a preselected direction relative to the rotation of the inputshaft 26. In the illustrated preferred embodiment, uni-directional freewheeling mechanisms 28a-28d are each oriented so as to permit each oftheir respective input gears 30a-30d to freely rotate about input shaft26 when the respective input gear 30 rotates in a clockwise directionrelative to the rotation of input shaft 26. At the same time, eachuni-directional free wheeling mechanism 28a-28d is held in constantmutual engagement with input shaft 26 and its respective input gear30a-30d so as to automatically lock its respective input gear 30a-30d toinput shaft 26 at all other times. For example, if a particular inputgear is rotating clockwise at a speed greater than the clockwiserotational speed of input shaft 26, the particular input gear isrotating clockwise relative to the rotation of input shaft 26. Thus, theparticular input gear will freely rotate about input shaft 26.Alternatively, if a particular input gear 30 is rotating clockwise at aspeed less than the clockwise rotational speed of input shaft 26, theparticular input gear 30 is rotating counterclockwise relative to therotation of input shaft 26. Thus, the particular input gear will beautomatically coupled or locked to input shaft 26. Depending upon therelative rotational direction of gears 30a-30d, each uni-directionalfree wheeling mechanism 28a-28d will individually lock its correspondinggear 30a-30d to input shaft 26 or permit its corresponding gear tofreely rotate about input shaft 26. Each gear 30 is either locked toinput shaft 26 such that power is transmitted from input shaft 26 to theparticular gear 30 or gear 30 is allowed to freely rotate about inputshaft 26 such that power would not be transmitted from input shaft 26 tothe particular input gear 30. As a result, when a plurality of gears30a-30d are coupled by their respective connector gears 40 to theirrespective output gears 36, uni-directional free wheeling mechanisms 28couple only the slowest rotating plurality of gears 30a-30d to inputshaft 26. Accordingly, when a plurality of gears 30a-30d are coupled bytheir respective connector gears 40 to their respective output gears 36to form gear trains, uni-directional free wheeling mechanisms willcouple only the fastest gear train between input shaft 26 and outputshaft 32. The remaining gear trains free wheel. Uni-directional freewheeling mechanisms 28a-28d permit a plurality of input gears 30a-30d tobe interconnected to a plurality of output gears 36 at the same timewhile only one input gear 30 is actually locked or coupled to inputshaft 26. Because a plurality of input gears 30 may be interconnected toa plurality of output gears 36 without locking up the transmission,shifting between gear sets 38 to change gear speeds may be done undercontinuous power.

Input gears 30a-30h are an array of differently sized toothed wheels orgears encircling input shaft 26. Each gear 30 preferably includes teethalong its outer perimeter for engaging with one of connector gears 40.Gears 30 have selectively sized radii for providing different speedratios when gears 30 are connected to output gears 36. Input gears 30are spaced apart from output gears 36, but are sized and positioned withrespect to output gears 36 so that input gears 30 may be connected tooutput gears 36 by connector gears 40. In the preferred embodiment,input gears 30 have teeth for engaging with the corresponding teeth ofconnector gears 40. As can be appreciated, other mechanisms may be usedto engage input gears 30 with the connector gears 40. Each input gear 30is in alignment with a corresponding output gear 36 to form gear sets38a-38h (shown in FIG. 2).

Output shaft 32 is preferably made from a high strength material, suchas steel, capable of withstanding large amounts of torque. Output shaft32 projects out of housing 24 and is coupled to a sprocket coupled tothe rear wheel of a bicycle or other means for transferring therotational motion of output shaft 32 to a desired location. Output shaft32 carries uni-directional free wheeling mechanisms 28e-28h and array ofoutput gears 36e-36h (shown in FIG. 2).

Uni-directional free wheeling mechanisms 28e-28h are integral with orare fixedly coupled to output shaft 32 between output shaft 32 at leastone of output gears 36e-36h. Uni-directional free wheeling mechanisms28e-28h are substantially identical to uni-directional free wheelingmechanisms 28a-28d except that each uni-directional free wheelingmechanism 28e-28h is oriented so as to permits its respective outputgear 36e-36h to freely rotate about output shaft 32 when its respectiveoutput gear 36 rotates in a counterclockwise direction relative to therotation of the output shaft 32. At the same time, each uni-directionalfree wheeling mechanism 28e-28h is held in constant mutual engagementwith output shaft 32 and its respective output gear 36e-36h so as toautomatically lock its respective output gear 36e-36h to output shaft 32at all other times. As a result, when a plurality of gears 36 are beingdriven their respective connector gears 40, uni-directional freewheeling mechanisms 28 couple only the fastest of gears 36 to outputshaft 32. Accordingly, when a plurality of gears 36e-36h are coupled bytheir respective connector gears 40 to their respective input gears 30to form gear trains, uni-directional free wheeling mechanisms willcouple only the fastest gear train between output shaft 32 and inputshaft 26. The remaining gear trains free wheel. Uni-directional freewheeling mechanisms 28e-28h permit a plurality of input gears 30e-30h tobe interconnected to the plurality of output gears 36e-36h at the sametime while only one output gear 36 is actually locked to output shaft32. Because the plurality of input gears 30e-30h may be interconnectedto a plurality of output gears 36e-36h without locking up thetransmission, shifting between gear sets 38e-38h to change gear speedsmay be done under continuous power.

Output gears 36 are an array of differently sized toothed wheels orgears encircling output shaft 32. Output gears 36a-36h (best shown inFIG. 2) are carried by and rotatably encircle output shaft 32. Gears36a-36h have selectively sized radii for providing a plurality ofdifferent speed ratios when gears 36 are connected to input gears 30.Output gears 36 are spaced apart from input gears 30, but are sized andpositioned with respect to input gears 30 so that output gears 36 may beconnected to input gears 30 by connector gears 40. In the preferredembodiment, output gears 36 have teeth for engaging with correspondingteeth of connector gears 40. As can be appreciated, other mechanisms maybe used to engage output gears 34 with connector gears 40. Each outputgear 36 is in alignment with a corresponding input gear 30 to form gearsets 38a-38h (shown in FIG. 2).

Connector gears 40 preferably comprise a plurality of toothed wheels ofthe same diameter. Connector gears 40 can be made from a variety ofdifferent materials including steel or high strength plastic. Connectorgears 40 are rotatably mounted and supported by shifting mechanism 42 soas to be movable into mutual rotatable engagement with input gears 30and output gears 36. Each connector gear 40 corresponds to a gear setformed by corresponding input gears 30 and output gears 36. When inmutual engagement with input gears 30 and output gears 36, connectorgears 40 transfer power from input gears 30 to output gears 36. Eachconnector gear 40 is rotatably mounted to shifting mechanism 42 so as tobe individually movable into mutual engagement with input gears 30 andoutput gears 36. As a result, a single gear set 38 or a plurality ofgear sets 38 may be engaged at once by a single connector gear 40 or aplurality of connector gears 40, respectively. Because a plurality ofconnector gears 40 may be engaged with the plurality of gear sets 38 atthe same time, power transfer between input shaft 26 and output shaft 32is continuous even during shifting between different gear sets 38 toprovide different speed ratios. Connector gears 40 are all preferably ofthe same size, and speed ratios are solely controlled by the size ofinput gears 30 and output gears 36 of each gear set 38.

In addition, because connector gears 40 are used to interconnect inputgears 30 and output gears 36 and because input gears 30 and output gears36 are spaced apart from one another, the radii of the input gears 30and output gears 36 may be independently sized to provide tailored speedratios and progressive power curves for different applications. Forexample, when transmission 20 is used in conjunction with a bicycle,different speed ratios and power curves may be provided for differentbicycle uses such as racing, touring, mountain or trail riding, andstreet riding. Because the input gears 30 and output gears 36 do notengage one another, their diameters are not restricted to presetshaft-to-shaft dimensions. The potential number of gear sets and speedratios is merely limited by the overall width of the transmission 20 andthe required width of gears 30, 36 and 40.

Furthermore, because input gears 30 and output gears 36 are spaced apartfrom one another and are only interconnected when the particular gearset 38 is engaged by a connector gear 40, transmission 20 produceslittle friction and reduces wasted effort on the part of the rider.Because uni-directional free wheeling mechanisms 28a-28d lock, at most,two of their corresponding gears to input shaft 26 during shifting, theremainder of their corresponding gears encircling uni-directional freewheeling mechanisms 28a-28d freely rotate about input shaft 26.Similarly, because uni-directional free wheeling mechanisms 28e-28hlock, at most, only two of their corresponding gears to output shaft 32during shifting, the remainder of the corresponding gears encirclinguni-directional free wheeling mechanisms 28e-28h freely rotate aboutoutput shaft 32. As a result, input shaft 26 engages and drives, atmost, two gear sets 38 during shifting. At all other times, input shaft26 merely engages and drives a single gear set 38. Generally, outputshaft 32 engages and drives, at most, two gear sets. Consequently,transmission 20 does not require large amounts of energy necessary forcontinuously rotating all the gear sets. Thus, transmission 20 providesmultiple speed ratios in an enclosed protected housing while reducingthe amount of energy required to rotate input shaft 26.

Shifting mechanism 42 selectively positions connector gears 40 in mutualrotary engagement with input gears 30 and output gears 36 and includesyokes 46a-46d and yokes 46e-46h (best shown in FIGS. 5-7), yoke pivotrods 48a, 48b, yoke springs 50a-50h, retainer 52 having retainer ends52a, 52b and selector cam 56. Yokes 46a-46h are generally elongated thinmembers which are provided for pivotally and rotatably supporting eachconnector gear 40. Yokes 46a-46h each include a pivot end 58, aconnector end 60 and a cam lobe contact 62. Pivot end 58 of each set ofyokes 46a-46h defines an aperture 64 for receiving one of yoke pivotrods 48a, 48b. As a result, yokes 46a-46h pivot about aperture 64 andyoke pivot rods 48a, 48b such that connector gears 40 pivot into and outof engagement with input gears 30 and output gears 36.

Connector end 60 of each yoke 46a-46h defines an aperture 66 forreceiving gear pins 68 which rotatably mount connector gears 40 to yokes46a and yokes 46b. Gear pins 68 preferably comprise flush bearing pins.As a result, connector gears 40 are rotatable so as to transmitrotational motion from input gears 30 to output gears 34 when in mutualengagement with input gears 30 and output gears 34. Apertures 66 extendthrough connector end 60 of yokes 46a-46h and are preferably located atvarious positions so as to cause connector gears 40 to be moved intomutual engagement with the various combinations of differently sizedinput gears 30 and output gears 36 of gear sets 38.

The body of each yoke of yokes 46a-46h is preferably shaped so as toaccommodate necessary locations of apertures 66 as well as gear pin 68and connector gear 40. In the depicted preferred embodiment, each yokeis identically shaped for ease of manufacture and assembly. However, ascan be appreciated, each yoke may alternatively have a unique shape foraccommodating the necessary location of aperture 66 and gear pin 68needed to position its respective connector gear 40 in mutual engagementwith the particular gear set 38.

Cam lobe contacts 62 project forwardly (towards the front of thebicycle) from the body of each of yokes 46a-46h. In the preferredembodiment, cam lobe contact 62 is an elongate finger. Cam lobe contacts62 of yokes 46a-46h are preferably aligned with one another andpositioned along the longitudinal length of selector cam 56. Cam lobecontacts 62 are engaged by selector cam 56 so as to pivot yokes 46a-46habout yoke pivot rods 48a, 48b such that connector gears 40 are alsopivoted into mutual engagement with the various gear sets formed byinput gears 30 and output gears 34.

Yoke pivot rods 48a, 48b extend through apertures 64 of yokes 46a-46h topivotally mount yokes 46a-46h to housing 24. In addition, as shown byFIG. 7, yoke pivot rods 48a and 48b extend through housing 24 endreceive fasteners 70 which are screwed onto the ends of yoke pivot rods48a, 48b to secure left and right casings of assembled housing 24 inplace.

Yoke springs 50a-50h are preferably flat leaf-springs which have a firstend coupled to pivot end 58 of yokes 46a-46h and have a second endengaging retainer ends 52a, 52b. Yoke springs 50a-50h spring load orbias connector end 60 of yokes 46a-46h and its corresponding connectorgear 40 out of engagement with gear sets 38.

Retainer ends 52a, 52b are preferably positioned near the top and bottomof transmission 20 above and below springs 50a and springs 50b,respectively. Retainer ends 52a and 52b project above and below springs50a and 50b, respectively, within housing 24. As a result, retainer ends52a, 52b engage springs 50a-50h, so as to compress at least one ofsprings 50a-50h to pivot connector gears 40 out of engagement with thegear sets 38. In addition, retainer ends 52a, 52b hold springs 50a, 50bin position during assembly of transmission 20 so that each spring 50a,50b does not need to be compressed when inserting shifting mechanism 42into housing 24.

Selector cam 56 is positioned and enclosed within housing 24 inalignment with cam lobe contacts 62 of yokes 46a46h. Selector cam 56 isgenerally an elongate cam which, upon being selectively rotated, engagescam lobe contacts 62 of yokes 46a-46h so that at least one of yokes46a-46h and its corresponding connector gear 40 is maintained in mutualengagement with a corresponding gear set 38 comprising one of inputgears. 30 and one of output gears 36. Because at least one of yokes46a46h and its corresponding connector gear 40 is always maintained inengagement with the gear set formed from input gears 30 and output gears34, power is continuously transmitted from input shaft 26 to outputshaft 32. During shifting between gear sets to change speed ratios,selector cam 56 is configured such that a second connector gear 40 ispivoted into engagement with the successive gear set 38 formed from oneof input gears 30 and one of output gears 36 before the precedingconnector gear 40 is biased by one of springs 50a-50h out of engagementwith the preceding gear set 38. As discussed above, uni-directional freewheeling mechanisms 28a-28h permit a plurality of gear sets 38 to beinterconnected at once without transmission 20 locking up becauseuni-directional free wheeling mechanisms 28a-28h permit only one gearset to be locked between input shaft 26 and output shaft 32 to transferpower. As a result, transmission 20 provides tailored speed ratios andprogressive power curves as well as an enclosed, linearly sequencedtransmission that will shift under continuous power, have a minimumnumber of gears engaged at any one time, and will not require continuousadjustment.

FIG. 2 shows a sectional view of transmission 20 taken along lines 2--2of FIG. 1. FIG. 2 illustrates housing 24, retainer 52, input shaft 26,uni-directional free wheeling mechanisms 28a-28d, input gears 30a-30h,output shaft 32, uni-directional free wheeling mechanisms 28e-28h andoutput gears 36a-36h in greater detail.

II. Housing

As shown by FIG. 2, gearbox or housing 24 is a generally narrow ovalshaped gearbox which includes ring 80, left casing 82, right casing 84,and sleeve bearings 86, 87, 88 and 89. Ring 80 encircles transmission20. When transmission 20 is employed in a bicycle, ring 20 is preferablyfabricated as an integral part of the bicycle frame. Ring 20 may be madefrom a variety of materials, but is preferably made from the samematerial as that of the bicycle frame. Alternatively, ring 20 may bemounted to the bicycle frame in any conventional well-known manner.

Left casing 82 is a generally flat oval shaped plate fitted within andsealed to ring 80. Left casing 82 includes openings 92, 94 and ridge 96.Openings 92 and 94 extend through left casing 82 and are located andsized for the reception of sleeve bearings 86, 87, input shaft 26 andoutput shaft 32. Preferably, openings 92 and 94 are sized to form atight fit with sleeve bearings 86 and 87, respectively, to form a tightseal so as to prevent road elements and contaminants from entering theinterior of housing 24. Ridge 96 encircles the perimeter of left casing82. Ridge 96 insets within ring 80 to seal between left casing 82 andring 80 and to properly align inner components contained within housing24. Left casing 82 is preferably mounted to ring 80 and may be formedfrom a different material such as injected plastic. Alternatively, leftcasing 82 may be formed integrally with ring 80.

Right casing 84 is a generally oval shaped plate having a perimeteridentical to left casing 82. Right casing 84 includes flange 97, opening98 and ridge 100. Flange 97 is integrally molded as part of right casing84 and defines a cavity 102 sized for reception of sleeve bearing 85.Flange 97 supports sleeve bearing 86 and an end of output shaft 32within housing 24 while preventing contaminants from entering intohousing 24.

Similar to opening 94, opening 98 extends through right casing 84 and issized and located for the reception of sleeve bearing 89 and input shaft26. Preferably, opening 98 is sized so as to form a tight fit or sealwith sleeve bearing 89 to prevent contaminants from entering theinterior of housing 24.

Ridge 100 is similar to ridge 96 and extends along an outer perimeter ofright casing 84. Ridge 100 insets within ring 80 so as to form a tightseal with ring 80 and to properly align the components of transmission20 partially supported by right casing 84.

Sleeve bearings 86, 87, 88 and 89 are conventionally known and aremounted within apertures 92, 94, cavity 102 of flange 96 and aperture98, respectively. Sleeve bearings 86 and 88 are aligned opposite oneanother and are supported by left casing 82 and right casing 84,respectively. Sleeve bearings 86 and 88 support and guide the rotationof output shaft 32. Sleeve bearing 86 also seals around output shaft 32to prevent elements from entering the interior of housing 24. Sleevebearings 87 and 89 are aligned opposite one another and are supported byleft casing 82 and right casing 84, respectively. Sleeve bearings 87 and89 support and guide the rotation of input shaft 26. In addition, sleevebearings 87 and 89 also seal around input shaft 26 to prevent elementsfrom entering the interior of housing 24. As can be appreciated, anybearing mechanisms such as ball bearings may be used in lieu of sleevebearings 86, 87, 88 and 89 for rotatably supporting input shaft 26 andoutput shaft 32.

As best shown by FIGS. 2 and 7, retainer 52 is a generally shell-shapedmember used for holding and aligning components of transmission 20 inplace during assembly. Retainer 52 includes retainer ends 52a, 52b andopenings 104, 106, 108 and 109. As discussed earlier, retainer ends 52a,52b hold springs 50a, 50b in position during assembly of transmission 20so that each spring 50a, 50b does not need to be compressed wheninserting shifting mechanism 42 into housing 24.

As shown in FIG. 2, openings 104 and 106 extend through the right sideof retainer 52. Opening 104 is sized and positioned for receiving outputshaft 32 and sleeve bearing 88. Opening 106 is sized and positioned forreceiving input shaft 26 and a portion of uni-directional free wheelingmechanisms 28a-28d. Openings 104 and 106 are sized so as to aid in thealignment of shafts 26 and 32, respectively, and the other componentswithin housing 24 during assembly.

As shown in FIG. 7, openings 108 and 109 extend through the right sideof retainer 52. Openings 108 are positioned near retainer ends 52a and52b and are sized for receiving and aligning yoke pivot rods 48a and48b. Opening 109 is located and sized for receiving an end of selectorcam 56. Opening 109 aligns selector cam 56 within housing 24 duringassembly. As a result, retainer 52 enables the components oftransmission 20 to be more easily assembled and aligned with oneanother. Retainer 52 is preferably attached to left casing 82 by screws107. Screws 107 extend through retainer 52 and threadably engage leftcasing 82 to secure retainer 52 in the desired position.

As discussed above, the present invention may have a variety of shapes,configurations and uses. However, for illustration purposes, the presentinvention is depicted as part of a bicycle transmission. Accordingly, asshown by FIG. 2, input shaft 26 is coupled to left pedal crank 110 andright pedal crank 111. Left and right pedal cranks 110, 111 are rotatedby the bicycle rider to provide power to input shaft 26. As can beappreciated, power may be supplied to input shaft 26 by various othermechanical and non-mechanical means. Output shaft 32 includes a threadedend 112 threadably mounted to an output or pedal hub sprocket 114. Inthe depicted embodiment of the present invention, pedal hub sprocket 114drives a chain (not shown) which engages a rear wheel sprocket (notshown) to transmit rotational motion from output shaft 32 to the rearwheel of the bicycle. As is conventionally known, the rear wheel hub ofthe bicycle may also have a conventional uni-directional free wheelingmechanism to allow the rider to cease pedalling and coast.

III. Input and Output Gears

As best shown by FIG. 2, input gears 30a-30h and output gears 36a-36hare carried by and rotatably encircle input shaft 26 and output shaft32, respectively. Input gears 30e-30h and output gears 36a-36d arepreferably fixedly secured to input shaft 26 and output shaft 32,respectively and abut one another to provide a more compact transmission20. In contrast, input gears 30a-30d and output gears 36e-36h arereleasably coupled to input shaft 26 and output shaft 32 byuni-directional free wheeling mechanisms 28a-28d and 28e-28f,respectively. Although compactly positioned adjacent one another, inputgears 30a-30b and output gears 36e-36h are sufficiently spaced from oneanother so that each gear may freely and independently rotate withrespect to adjacent gears.

As further shown by FIG. 2, input gears 30 have radii which generallydecrease towards left casing 82. Output gears 36 correspond to eachinput gear 30 and have radii which increase towards left casing 82.Because input gears 30 and output gears 36 are opposingly arranged insize, transmission 20 is compact and takes up little space.Alternatively, input gears 30 and output gears 36 may be arranged in anydesired configuration to provide a tailored power curve. Each input gear30 is aligned with the corresponding output gear 36 to provide aplurality of gear sets 38a-38h. Each gear set 38a-38h provides adifferent speed ratio between input gear 30 and output gear 36. In thedepicted embodiment, gear set 38a provides the highest gear speed whilegear set 38h provides the lowest gear speed. In the depicted embodiment,gear sets 38a-38h are configured to provide the speed ratios and powercurve presented in Table 2. Table 2 lists the number of gear teeth foreach of the input gears 30 and output gears 36. Table 2 also illustratesthe overall speed ratio provided by each gear set 38 and the percent ofchange of overall speed ratio between adjacent gear sets 38.

                  TABLE 2                                                         ______________________________________                                        Speed Ratios and Percent of Change of the Preferred Embodiment                                   Output Gear                                                                             Overall Speed                                                                          Percent of                              Gear Set                                                                             Input Gear Teeth                                                                          Teeth     Ratio*   Change                                  ______________________________________                                        38h    30h     40      36h  80   1.00                                                                                   7.9                                 38g    30g     41      36g  76   1.08                                                                                   11.2                                38f    30f     45      36f  75   1.20                                                                                   15.0                                38e    30e     49      36e  71   1.38                                                                                   18.6                                38d    30d     54      36d  66   1.64                                                                                   26.4                                38c    30c     61      36c  59   2.07                                                                                   34.2                                38b    30b     68      36b  49   2.78                                                                                   44.1                                38a    30a     80      36a  40   4.00                                         ______________________________________                                         *(Pedal hub sprocket to rear hub sprocket ratio is 2:1)                  

As shown by Table 2, input gear 30h of gear set 38h has 40 gear teethwhile output gear 36h of gear set 38h has 80 gear teeth. Because thepedal hub sprocket to rear hub sprocket ratio is 2:1, gear set 38hprovides an overall speed ratio of 1.00. The next adjacent gear set 38ghas an input gear 30g with 41 gear teeth and an output gear 36g with 76gear teeth. Gear set 38g provides an overall speed ratio of 1.08 whichis a 7.9% change from the overall speed ratio provided by gear set 38h.As shown by Table 2, the depicted embodiment of transmission 20 providestailored speed ratios and a progressive power curve which provides alower percent of change between lower speed ratios and a higher "overdrive" percent of change between higher speed ratios. As can beappreciated, because input gears 30 and output gears 36 do not directlyengage one another and because their diameters are not restricted to apreset shaft-to-shaft dimension, the radii of input gears 30 and outputgears 36, the number of teeth on input gears 30 and output gears 36 andthe number of gear sets 38 may be varied to provide practically anytailored set of speed ratios and power curves for various applications.

IV. Free Wheeling Mechanisms

As further shown by FIG. 2, uni-directional free wheeling mechanisms28a-28d are coupled to input shaft 26 between input shaft 26 and inputgears 30 of gear sets 38a-38d. Uni-directional free wheeling mechanisms28e-28h are coupled to output shaft 32 between output shaft 32 andoutput gears 36 of gear sets 38e-38h. As a result, each gear set 38a-38his provided with at least one uni-directional free wheeling mechanismbetween a gear and the gear's respective shaft. As a result, any twogear sets 38 may be engaged by their corresponding connector gears 40(shown in FIG. 1) at the same time without transmission 20 jamming orlocking up. Consequently, at least one gear set 38 may be interconnectedby the connector 40 and locked to output shaft 32 at all times so thatshifting between gear sets 38 may be done under continuous power.

Uni-directional free wheeling mechanisms 28a-28h are each mounted totheir respective shafts between the respective shafts and the gearscarried by each shaft having the largest radii. In the depictedembodiment, uni-directional free wheeling mechanisms 28a-28d are mountedto shaft 26 adjacent input gears 30 of gear sets 38a-38d.Uni-directional free wheeling mechanisms 28e-28h are coupled to outputshaft 32 adjacent to output gears 36 of gear sets 38e-38h. Becauseuni-directional free wheeling mechanisms 28a-28h are mounted adjacent tolarger sized gears, uni-directional free wheeling mechanisms 28a-28h maybe sized larger so as to be able to better withstand larger amounts oftorque. Alternatively, uni-directional free wheeling mechanisms 28a-28hmay be coupled to input shaft 26 adjacent all of input gears 30 of gearsets 38a-38h or uni-directional free wheeling mechanisms 28a-28h may becoupled to output shaft 32 adjacent to all of output gears 36 of gearsets 38a-38h. In addition, uni-directional free wheeling mechanisms 28may be coupled to their respective shafts adjacent to any desired numberof the gears carried by the respective shaft so long as each gear setincludes at least one uni-directional free wheeling mechanism betweenone of the shafts and one of its gears.

FIGS. 3 and 4 illustrate the preferred embodiment of uni-directionalfree wheeling mechanisms 28a-28d in greater detail. As shown by FIGS. 3and 4, uni-directional free wheeling mechanisms 28a-28d include drum116, ratchets 118, loaded cam or pawls 120 and mounting wire 127. Drum116 is a single supporting structure for coupling to input shaft 26 andfor defining a single slot which is used for each and everyuni-directional free wheeling mechanism 28a-28d. Alternatively, eachuni-directional free wheeling mechanism 28a-28d may be provided with itsown individual drum with an individual slot or notch for receiving itsindividual pawl 120. In addition, drum 116 may alternatively beintegrally formed as part of input shaft 126.

As shown by FIG. 3, drum 116 is generally cylindrical shaped andincludes central bore 122, shoulder 124, slot 126 and mounting wire 127.Bore 122 extends through drum 116 and is sized for the reception ofinput shaft 26. Bore 122 is preferably shaped for being keyed with inputshaft 26. The circumference 123 extends around drum 116 and engagesratchets 118. Shoulder 124 is formed where circumference 123 projectsoutwardly. Shoulder 124 abuts a face of gear 30a to align and maintainthe gear 30a in proper position. Drum 116 defines slot 126 whichlongitudinally extends along and within circumference 123 of drum 116.In lieu of being defined by drum 116, slot 126 may alternatively beformed directly within input shaft 26. Slot 126 has a depth sufficientfor completely receiving each pawl 120. Slot 126 has a length positionedfor extending adjacent to input gears 30a-30d of gear sets 38a-38d. Inthe preferred embodiment, slot 126 includes channels 128 which extendinto a lower surface of slot 126. Channels 128 correspond to each gear30 and pawl 120. Channels 128 are sized for capturing one end of aspring mechanism of each pawl 120.

Mounting wire 127 is an elongated stiff wire which extends within slot126 and has a first end embedded in shoulder 124 of drum 116. Mountingwire 127 extends through each pawl 120 so as to secure each pawl 120 inplace within slot 126. Mounting wire 127 permits each pawl 120 toindividually rotate or pivot about mounting wire 127.

FIG. 4 shows an individual ratchet 118 and pawl 120 in greater detail.Ratchets 118 are slotted or serrated surfaces formed or machined alongan inner diameter of each of input gears 30a-30d of gear sets 38a-38d.Each ratchet 118 includes teeth 130 which define notches 132. Teeth 130are oriented or pointed in a generally counterclockwise direction.

Pawls 120 are generally oblong, oval shaped cams which are spring loadedinto engagement with ratchets 118. Each pawl 120 includes a pivot hole134, channel 136 and a spring mechanism 138. Pivot hole 134 extendsthrough pawl 120 and receives mounting wire 127 of drum 116. Pivot hole134 permits pawl 120 to pivotally rotate about mounting wire 127 withinslot 126. Channel 136 extends upward into a lower surface of each pawl120. Each channel 136 receives the first end of spring mechanism 138.Each spring mechanism 138 has a first end coupled to its respective pawl120 and a second end which engages drum 116. Preferably, the second endof each spring mechanism 138 is received within channel 128 definedwithin slot 126. As can be appreciated, spring mechanisms 138 may becoupled between pawls 120 and drum 116 by various attachment mechanisms.Spring mechanisms 138 preferably comprise coil springs. Alternatively,spring mechanisms 138 may comprise leaf springs or various other springmechanisms as are conventionally known. Spring mechanisms 138individually bias their respective pawls into engagement with eachpawl's respective ratchet 118.

As shown by FIG. 4, drum 116 is fixedly mounted to input shaft 26 sothat rotation of drum 116 also rotates input shaft 26. When a particularinput gear 30 and its corresponding ratchet 118 rotate clockwiserelative to the rotation of input shaft 26 and drum 116 (i.e., inputgear 30 rotates clockwise at a speed greater than the clockwise speed ofinput shaft 26 and drum 116), teeth 130 of ratchet 118 continuously movepawl 120 against the bias or load of spring mechanism 138 into slot 128so that pawl 120 does not lock within notches 132 of ratchet 118. As aresult, the particular input gear 30 is permitted to freely rotate aboutdrum 116 and input shaft 26. Alternatively, when the particular inputgear 30 rotates in a counterclockwise direction relative to the rotationof input shaft 26 and drum 116 (i.e., input gear 30 rotates clockwise ata speed less than the clockwise speed of input shaft 26 and drum 116),pawl 120 is biased into engagement with notches 132 of ratchet 118 byspring mechanism 138 such that pawl 120 locks input gear 30 to drum 116and input shaft 26. As a result, when the input gears 30a-30d of gearsets 38a-38d rotate at different speeds, because of different speedratios between gear sets 38a-38d, the input gear 30a-30d having theslowest speed will automatically be locked to drum 116 and input shaft26 by its corresponding uni-directional free wheeling mechanism 28a-28d.Consequently, when the plurality of input gears 30a-30d areinterconnected to a plurality of output gears 36 of gear sets 38a-38d atthe same time, uni-directional free wheeling mechanisms 28a-28dautomatically lock the slowest gear to input shaft 26 and disengages thefaster gear or gears from input shaft 26. The remainder of input gears30a-30d not coupled to a corresponding output gear 36 by a connectorgear 40 are locked or coupled to input shaft 26 by pawls 120 and rotatesat a speed equal to the speed of input shaft 26. As a result, adjacentgear sets 38 are being rotated at relatively the same speed when asuccessive adjacent connector gear 40 is being moved into engagementwith the successive adjacent gear set 38. Thus, shifting between gearsets 38 does not require the establishment of a neutral state, andshifting may be performed under full power.

Uni-directional free wheeling mechanisms 28e-28h are identical touni-directional free wheeling mechanisms 28a-28d except that ratchets118 have opposite orientations such that teeth 130 point clockwise.Pawls 120 are appropriately biased such that when the plurality of inputgears 30 are interconnected to a plurality of output gears 36 byconnector gears 40, uni-directional free wheeling mechanisms 28e-28hpermit gears 36e-36h to freely and individually rotate about drum 116and shaft 32 when each gear 36e-36h rotates counterclockwise relative todrum 116 and shaft 32.

V. Connector Gears and Yokes

FIGS. 5 and 6 illustrate connector gears 40, yokes 46e-46h and yokesprings 50e-50h in greater detail. FIG. 5 shows an end view of a singlerepresentative yoke 46h. FIG. 6 is a side view of connector gears 40rotatably mounted to yokes 46e-46h which carry yoke springs 50e-50h. Asdiscussed above, the yokes 46a-46d and springs 50a-50d are substantiallyidentical to the yokes 46e-46h and springs 50e-50h but are merelypivotally mounted to housing 24 about a different yoke pivot rod 48b. Asshown by FIG. 5, yokes 46e-46h are thin elongate plate-like membersincluding apertures 64, 66 and connector gear slot 140. Aperture 64extends through each yoke 46 and is sized for receiving its respectiveyoke pivot rod 48a or 48b. Each aperture 64 of each yoke 46e-46h is inalignment with aperture 64 of adjacent yokes 46e-46h. As a result, asingle yoke pivot rod 48a is inserted through aperture 64 such that eachyoke 46e-46h pivots so as to move connector gears 40 into and out ofengagement with gear sets 38.

Aperture 66 extends through connector end 60 and is sized for receivinggear pin 68 so as to rotatably support one of connector gears 40. Unlikeaperture 64, the location of aperture 66 within connector end 60 of eachyoke 46e-46h varies depending upon the diameter of input gears 30 andoutput gears 36 of the corresponding gear set 38 and diameter ofconnector gear 40. Aperture 66 is located so that connector gear 40 isaccordingly positioned to be movable into mutual engagement with inputgear 30 and output gear 36 of the corresponding gear set 38.

Connector gear slot 140 extends upward and through connector end 60 ofeach yoke 46e-46h. Connector gear slot 140 preferably has a widthslightly greater than the width of connector gear 40 so that connectorgear 40 may freely rotate within connector gear slot 140. Each yoke46e-46h is slightly narrower than the spacing of gears 30 and gears 36so as to allow yokes 46e-46h to move individually. Yokes 46e-46h arerotatably mounted between left casing 82, right casing 84 and retainer52a to maintain a proper vertical alignment.

FIG. 6 is a side view of yokes 46e-46h carrying yoke springs 50e-50h andconnector gears 40. For ease of illustration, each yoke 46, connectorgear 40 and spring 50 is shown offset from adjacent yokes 46, gears 40and springs 50. Yokes 46a-46d are identical to yokes 46e-46h but arepivoted about yoke pivot rod 48b instead. As best shown by FIG. 6, eachconnector gear 40 is rotatably coupled to an individual yoke 46e-46h bythe gear pin 68 through aperture 66 within each of yokes 46e-46h. Eachaperture 66 and gear pin 68 rotatably support the connector gear 40 atvarious locations along each one of yokes 46e-46h so that thecorresponding connector gear 40 is moved into mutual engagement with thevarious combinations of differently sized input gears 30 and outputgears 36.

Yokes 46e-46h are shaped to accommodate the various necessary locationsof apertures 66 and gear pins 68, apertures 64, yoke pivot rod 48a, andcam lobe contacts 62. Accordingly, yokes 46 may have any shapeencompassing these three points. In the preferred embodiment shown, eachof yokes 46e-46h has a generally trapezoidal shaped body which includesrear edge 142, front edge 144 and top and bottom edges 146, 148. Top andbottom edges 146 and 148 diverge away from one another from rear edge142 towards front edge 144 to give each yoke 46a its trapezoidal shape.As a result, front edge 144 is longer than rear edge 142 so that frontedge 144 may accommodate the various locations of apertures 66 and gearpins 68. Front edge 144 is preferably concave so that only a smallradial portion of each connector gear is disposed within connector slot140 (shown in FIG. 5) and so that the main body of each of yokes 46e-46hdoes not contact gear sets 38 during the movement of connector end 60 ofeach of yokes 46e-46h towards gear sets 38. As a result, connector end60 of each of yokes 46e-46h may be pivoted a larger distance forward sothat smaller connector gears 40 may be used to interconnect gear sets 38having differently sized input gears 30 and output gears 36. As can beappreciated, yokes 46a-46h may have any one of a variety alternateshapes and configurations for pivotally and rotatably supportingconnector gears 40.

VI. Selector Cam

FIGS. 7-9 show selector cam 56 in greater detail. FIG. 7 shows asectional view of transmission 20 taken along lines 7--7 of FIG. 1. FIG.8 shows selector cam 56 in engagement with cam lobe contact 62 of yoke46h. FIG. 9 shows a side view of selector cam 56 in operationalengagement with shifters 150a and 150b. As best shown by FIG. 7,selector cam 56 includes cam shaft 152, bearings 153, 154, cam disk 156and index 157. Cam shaft 152 is generally an elongated cylinder whichtraverses each one of yokes 46a-46h and their corresponding cam lobecontacts 62. Cam shaft 152 has opposite ends which are rotatably coupledto right casing 84 and left casing 82 by bearings 153 and 154,respectively. Bearings 153 and 154 preferably comprise sleeve bearings,as are conventionally known, which are secured within cavities definedby left casing 82 and right casing 84. As can be appreciated, otherbearing mechanisms such as ball bearings may be used in lieu of sleevebearings 153 and 154 for rotatably supporting cam shaft 152 withinhousing 24.

Cam shaft 152 carries a plurality of cam lobes 158a-158h. Each cam lobe158 corresponds to and is in alignment with an individual cam lobecontact 62 of one of yokes 46a, 46h. Cam lobes 158a-158h (best shown inFIG. 8) are axially and radially spaced from one another about cam shaft152. Each cam lobe 158 includes an outer surface 160 and an innersurface 162. Outer surface 160 of each cam lobe 158 engages cam lobecontact 62 (shown in FIGS. 6 and 8) of one of yokes 46a-46h so that aconnector gear 40 carried by one of the yokes 46a-46h interconnects thecorresponding gear set 38. Inner surface 162 of each cam lobe engagescam lobe contact 62 of one of yokes 46a-46h to permit cam lobe contact62 and its corresponding yoke 46a-46h to be retracted out of engagementwith the corresponding gear set 38 by the biasing force of itscorresponding spring 50a-50h. Alternatively, yokes 46a-46h, connectorgears 40 and springs 50a-50h may be configured and located such thatsprings 50a-50h bias connector gears 40 into engagement with gear sets38 wherein selector cam 56 selectively engages yokes 46a46h to moveyokes 46a-46h and their respective connector gears 40 out of engagementwith gear sets 38. Rotation of cam shaft 152 causes at least one camlobe 158 to engage a corresponding cam lobe contact 62 so that at leastone yoke 46 and its corresponding connector gear 40 is moved intoengagement with a selected gear set 38. In the preferred embodiment, camlobes 158 are axially and radially spaced so that adjacent yokes 46 andconnector gears 40 may be sequentially actuated towards or away fromcorresponding adjacent gear sets 38. As a result, selector cam 56provides sequential shifting between adjacent gear sets 38.Alternatively, other mechanisms may be used in lieu of selector cam 56to sequentially actuate or move non-adjacent yokes 46 and connectorgears 40 in and out of engagement with non-adjacent gear sets 38. Forexample, shifting mechanisms may alternatively be provided forsequentially actuating non-adjacent yokes 46h and 46f to shift directlybetween gear sets 38h and 38f without the need for engaging gear set38g.

As best shown by FIG. 8, each lobe partially encircles cam shaft 152 andhas an outer surface 160 overlapping the outer surfaces 160 of adjacentcam lobes 158. As a result, outer surfaces 160 of adjacent lobes maysimultaneously contact cam lobe contacts 62 of two adjacent yokes 46 topivot their two respective connector gears 40 into engagement with theirtwo respective gear sets 38. Consequently, the first connector gear 40may be pivoted into mutual engagement with gear set 38 before a secondalready engaged connector gear 40 is moved out of engagement with itsrespective gear set 38. Continued rotation of cam shaft 152 causes thesecond already engaged connector gear 40 to become disengaged. As aresult, lobes 158 of cam shaft 152 move connector gears 40 so that atleast one connector gear 40 is always interconnecting a gear set 38 toprovide continuous power even during shifting between gear sets 38. Asdiscussed above, uni-directional free wheeling mechanisms 28 preventtransmission 20 from locking up when the first and second gear sets 38are engaged by connector gears 40 simultaneously.

As shown by FIG. 7, cam shaft 152 is preferably keyed to cam disk 156such that rotation of cam disk 156 rotates cam shaft 152. As a result,cam shaft 152 and its corresponding lobes 158a-158h may be selectivelyrotated so as to shift different connector gears 40 into engagement withgear sets 38 by rotation of cam disk 156. Cam disk 156 is preferablypositioned adjacent to left casing 82 which is preferably shaped so asto completely enclose cam disk 156. Cam disk 156 is keyed to an end ofcam shaft 152 and includes tracks 166, 168. Tracks 166 and 168 extendalong an outer perimeter of cam disk 156. The outer circumferentialsurface of track 166 defines slots 170. Slots 170 are sized forreceiving and engaging shifter 150a (shown in FIG. 9). Slots 170 arespaced and positioned about cam disk 156 to correspond to the selectedrotational positions of lobes 158a-158h. Similarly, track 168 includesslots 172. Slots 172 extend into the surface of track 168 and are sizedfor engaging with shifter 150b (shown in FIG. 9). Slots 172 are alsospaced and positioned about cam disk 156 to correspond with selectedrotational orientations of lobes 158a-158h. In the preferred embodiment,slots 170 are used to rotate cam shaft 152 counterclockwise while slots172 are used to rotate cam shaft 152 clockwise for down shifting and upshifting, respectively.

Index 157 includes indentations 174, notch 175, spring 176 and bead 178.Indentations 174 extend into the face of cam disk 156 and are spaced atselected locations about a circumference of cam disk 156 correspondingto cam disk positions for different gear speeds. Notch 175 extends intoleft casing 82 and contains spring 176 and bead 178. Spring 176 biases asurface of bead 178 into engagement with the face of cam disk 156. Notch175 is aligned with indentations 174 so that spring 176 forces bead 178into releasable engagement with indentations 174. As a result, index 157indicates precise cam disk locations for selecting different speedratios by rotating cam disk 156. Index 174 also aids in maintaining camdisk 156 in a selected radial position.

FIG. 9 further illustrates shifters 150a and 150b. FIG. 9 illustratesshifters 150a and 150b in engagement with cam disk 156 for rotation ofcam shaft 152 to shift between speed ratios by interconnecting differentgear sets 38 with connector gears 40. As shown by FIG. 9, shifter 150bincludes an upshift cable housing 180, upshift cable 182, stop bead 184and shift bead 186, while shifter 150a includes downshift cable housing188, downshift cable 190, stop bead 192 and shift bead 194. Upshiftcable housing 180 encloses upshift cable 182 which ultimately is coupledto one of two thumb levers (not shown) mounted conveniently near thehandlebar grips of the bicycle in which transmission 20 is employed.Upshift cable 182 preferably comprises typical bicycle cable as isconventionally used in bicycles. Stop bead 184 and shift bead 186 aresecured to the lower end of cable 182 outside of cable housing 180. Stopbead 184 and shift bead 186 are held against cam disk 156 so as toengage slots 172 by cable 182. FIG. 9 shows shift bead 186 in a fullyengaged position within slots 172 just before the corresponding thumbshift lever is released. FIG. 9 also shows shift bead 194 in a neutralposition before any down shifting of cam disk 156. Shift beads 186 and194 are preferably maintained in engagement with tracks 168 and 166 ofcam disk 156 by the stiffness of cables 182 and 190, respectively.

Shift bead 186 is sized for reception within slots 172 and engages slots172 to rotate cam disk 156 in a clockwise direction so that asuccessively higher cam lobe 158 is rotated to engage its correspondingyoke 46 and to move the yoke's connector gear 40 into engagement with asuccessively higher gear set 38 having a higher speed ratio. Continuedrotation of cam disk 156 also causes the presently engaged cam lobe 158to rotate so that its corresponding yoke 46 and connector gear 40 areretracted out of engagement with the presently engaged gear set 38. Asdiscussed above, because adjacent lobes 158 radially overlap oneanother, a successive gear set will be in engaged before the precedinggear set is completely disengaged by connector gears 40. Stop bead 184is sized larger than the opening of upshift cable housing 180. Stop bead184 is spaced from shift bead 186 at a selected distance to limit thedegree by which cam disk 156 is rotated with a single shifting action.

Down shift cable housing 188, down shift cable 190, stop bead 192 andshift bead 194 perform similar functions to housing 180, cable 182 andbeads 184, 186, respectively. However, shift bead 194 engage slots 170to rotate cam disk in an opposite, counterclockwise direction to rotatecam lobes 158 such that a successively lower cam lobe 158 engages one ofyokes 46a, 46h and the presently engaged cam lobe 158 disengages itscorresponding yoke. As a result, one of connector gears 40 interconnectsthe next successively lower gear set 38 while the presently engagedconnector gear 40 is retracted from the preceding higher gear set 38upon continued rotation of cam disk 156.

VII. Operation

In operation, speed ratios between the input shaft 26 and output shaft32 are changed by actuation of shifters 150a and 150b. Depending uponthe desired direction of shifting, either shift bead 158 or shift bead166 will engage its corresponding slot 170 or slot 172 to rotate camdisk 156 in a counter clockwise direction or clockwise direction,respectively. Rotation of cam disk 156 also rotates cam shaft 152 andits corresponding cam lobes 158 so that the outer surface 160 of thenext successive cam lobe 158 is brought into engagement with itscorresponding cam lobe contact 62 of the next successive yoke 46. As aresult, the next successive yoke 46 and its corresponding connector gear40 are moved against the spring biasing force of the particular yokespring 50 into mutual engagement with the corresponding next successivegear set 38. Because cam lobes 158 are radially located about cam shaft152 so as to partially overlap one another, the next successiveconnector gear 40 is moved into engagement with its corresponding gearset 38 before the preceding connector gear 40 is retracted out ofengagement with its respective gear set 38 by one of springs 50a-50h.Although the preceding and the successive connector gears 40simultaneously interconnect different gear sets 38 which have differentrotational speeds, transmission 20 does not lock up because freewheeling uni-directional mechanisms 28 couple only one gear to theirrespective input and output shafts when a plurality of gears arerotating about the respective input and output shafts at differentspeeds. As a result, only one gear set 38 is permitted to transfer powerfrom input shaft 26 to output shaft 32 at any particular moment. Becausethe successive gear set is interconnected by connector gear 40 beforethe preceding gear set 38 is disconnected, shifting is performed underfull continuous power without a neutral stage. Continued activation ofshifter 150a or 150b causes further rotation of cam disk 156 and furtherrotation of cam shaft 152 to cause the preceding cam lobe 158 to rotateto a preselected position so that cam lobe contact 62 and its respectiveyoke 46 will be biased by spring 50 into engagement with inner surface162 of the preceding lobe 158. Consequently, the further rotation of camdisk 156 and cam shaft 152 completes the shifting between gear sets 38by causing the preceding connector gear 40 to be retracted out ofengagement with its respective preceding gear set 38 after thesuccessive gear set 38 has been connected by a connector gear 40.Completion of shifting between gear sets 38 is indicated when eitherstop bead 184 or stop bead 192 abuts housing 180 or housing 188,respectively, depending upon the direction of shift. Completion ofshifting is further indicated by bead 178 engaging indentation 174 ofindex 157. As can be appreciated, any one of a variety of mechanisms maybe used to index the rotation of cam disk 156 and cam shaft 152 toindicate completion of shifting between gear sets 138. In addition,other mechanisms may alternatively be used to provide controlledrotation of cam shaft 152 such as hydraulic/pneumatic controls,actuators and the like.

VIII. Alternate Wheel Hub Transmissions

FIGS. 10-12 illustrate transmission 220, an alternate embodiment oftransmission 20 depicted in FIGS. 1-9. For purposes of illustration,transmission 220 is depicted as part of a bicycle 221 including a frame222, front wheel 223, rear wheel 225, left and right pedal cranks 210,211, drive sprocket 227, rear wheel sprocket 229 and chain 231. Asconventionally known, frame 222 rotatably supports front wheel 223 andrear wheel 225. With respect to rear wheel 225, frame 222 includes dropouts 235 which are coupled, preferably by bolting, to axle 239 of wheel225. In addition to axle 239, rear wheel 225 includes a hub 241, spokes243, rim 245 and tire 247. Drive sprocket 227 is coupled to left andright pedal cranks 210 and 211. Rear wheel sprocket 229 is coupled torear wheel 225. Chain 231 interconnects drive sprocket 227 and rearwheel sprocket 229 to transfer power from drive sprocket 227 to rearwheel sprocket 229. Rear wheel sprocket 229 is coupled to an input shaft226 of transmission 220. As a result, rotation of left and right pedalcranks by the bicycle rider provide power to input shaft 226 oftransmission 220. Transmission 220 transmits power from input shaft 226to rear wheel 225. As can be appreciated, power may be supplied to inputshaft 226 by various other mechanical and non-mechanical means.Furthermore, transmission 220 may alternatively be utilized in othertypes of cycles having different wheel arrangements.

Transmission 220 is similar to transmission 20 depicted in FIGS. 1-9except that transmission 220 is configured for being constructed andassembled as part of a hub 241 of rear wheel 225. As with transmission20, transmission 220 includes input gears 230a-230l, output gears236a-236l, and uni-directional free wheeling mechanisms 228a-228l (shownin FIG. 11). As with transmission 20, transmission 220 also includesconnector gears 40 (shown in FIGS. 1, 6 and 7) and shifting mechanism 42(shown in FIGS. 1 and 5-9) for interconnecting input gears 230 andoutput gears 236 forming gear sets 238. As can be appreciated, each gearset 238 shown in FIG. 11 requires a corresponding connector gear 40supported by a yoke 46 (shown in FIG. 6). Connector gears 40 and theremaining components of shifter 42, including yokes 46 are housed andenclosed by housing 224. More particularly, housing 224 supports andencloses connector gears 40, yokes 46, yoke springs 50 and selector cam56 (previously described with respect to FIGS. 1 and 5-9). Similar toretainer 52 in left casing 82 and right casing 84 of transmission 20,housing 224 supports yoke pivot rods 48 which are coupled to yokes 46and connector gears 40. Actuation of cam 56 actuates a yoke 46 and acorresponding connector gear 40 into mutual engagement with acorresponding gear set 238. Because connector gears 40 and shifter 42are housed and supported by a casing specifically shaped to extendaround connector gears 40 and shifter 42 separate from input gears 230and output gears 236, the size and weight of hub 241 of wheel 225 isreduced as compared transmission 420 (shown in FIGS. 13 and 14) whichare enclosed by a single circular housing. As best shown by FIG. 10,transmission 220 is assembled as part of wheel 225 and is generallylocated at a center of wheel 225 where transmission 220 is supported byconventional wheel drop outs 235 of frame 222.

FIGS. 11 and 12 illustrate transmission 220 in greater detail. FIG. 11is a horizontal sectional view through input shaft 226 and axle 239illustrating transmission 220 in greater detail. FIG. 12 is an enlargedsectional view illustrating uni-directional free wheeling mechanisms 228in greater detail. Transmission 220 is similar to transmission 20depicted in FIGS. 1-9 except that transmission 220 is reconfigured forbeing constructed and assembled as part of wheel 225. Transmission 220is further reconfigured to reduce the overall weight of transmission220. For ease of illustration, those elements of transmission 220 whichare similar to corresponding elements of transmission 20 are numberedsimilarly. Transmission 220 includes fixed disc 282, axle 239, inputshaft 226, drum 316a, input gears 230a-230l, uni-directional freewheeling mechanisms 228g-228l, drum 316b, output gears 236a-236l, freewheeling mechanism 285, rotating disc 287, bearing/spoke ring 288,housing 224 (shown in FIG. 10), bearings 284, 286, 289, 291, 292,connector gears 40 (shown in FIG. 7) and shifting mechanism 42 (shown inFIGS. 1, 8 and 9). Fixed disc 282 is a hollow enclosure with a roundopening 283. Fixed disc 282 receives and substantially encloses inputgears 230 and output gears 236. Opening 283 is covered by rotating disc287. Fixed disc 282 is fixedly coupled to axle 239 which is stationarilycoupled to drop outs 235 of frame 222 (shown in FIG. 10). Fixed disc 282supports axle 239 and input shaft 226 to align transmission 220 withinwheel 225 as part of hub 241.

Axle 239 is an elongate axle rod extending through transmission 220.Axle 239 is stationarily supported by fixed disc 282 and extendsconcentrically through output gears 236a-236l, uni-directional freewheeling mechanisms 228a-228f, conventional free wheeling mechanism 285and rotating disc 291. Axle 239 provides an axis about which wheel 225rotates and an axis about which output gears 236a-236l, uni-directionalfree wheeling mechanisms 228a-228f, conventional free wheeling mechanism285 and rotating disc 287 rotate. Axle 239 includes drop out connectors293, 295 for mounting axle 239 and wheel 225 to frame 222 of bicycle221.

Input shaft 226 is fixedly coupled to rear sprocket 229 and extendsthrough fixed disc 282 and drum 316a. Input shaft 226 is rotatablycoupled to fixed disc 282 by bearings 284. Input shaft 226 is fixedlycoupled to drum 316a. As a result, rotation of rear sprocket 229 rotatesinput shaft 226 to further rotate drum 316a.

Drum 316a is a generally bell-shaped cone fixedly coupled to input shaft226. Similar to drum 116 (shown in FIGS. 3 and 4), drum 316a supports aplurality of input gears 230 about an input shaft 226 and furthersupports a plurality of uni-directional free wheeling mechanisms228g-228l for coupling input gears 230g-230l to drum 316a fortransmitting power from input shaft 226 to output gears 236g-236l,respectively. In addition, drum 316a also supports input gears230a-230f. Drum 316a is preferably formed from high-strength steel.

Input gears 230a-230l are an array of differently sized toothed wheelsor gears encircling drum 316a and input shaft 226. Each gear 230preferably includes teeth along its outer perimeter for engaging withone of connector gears 40. Gears 230 have selectively sized radii forproviding different speed ratios when gears 230 are connected to outputgears 236. Input gears 230 are spaced apart from output gears 236, andare sized and positioned with respect to output gears 236 so that inputgears 230 may be connected to output gears 236 by connector gears 40.Input gears 230a-230f are fixedly secured along an exterior surface ofdrum 316a. Input gears 230g-230l are coupled to an exterior surface ofdrum 316a by free wheeling mechanisms 228g-228l, respectively. Becausedrum 316a has an outer diameter which increases in size from input gear230a towards input gear 230l and because drum 316a has a hollowinterior, the overall weight of gears 230 and drum 316a is reduced toeffectively reduce the weight of transmission 220.

Uni-directional free wheeling mechanisms 228g-228l are substantiallyidentical to uni-directional free wheeling mechanisms 28 (shown in FIGS.3 and 4) except that uni-directional free wheeling mechanisms 228g-228lare supported by drum 316a in lieu of drum 116 (shown in FIG. 3). Asbest shown by FIG. 12, because of the sloped, stepped exterior surfaceof drum 316a, each pawl 120 of each mechanism 228g-228l is provided withits own individual mounting wire 327 which secures each pawl in placewithin an individual slot 326 formed within the exterior surface of drum316a. Uni-directional free wheeling mechanisms 228g-228l functionidentically to uni-directional free wheeling mechanisms 28a-28d. When aplurality of input gears 230g-230l are interconnected to a plurality ofoutput gears 236g-236l of gears sets 238 at the same time,uni-directional free wheeling mechanisms 228g-228l automatically lockthe slowest gear to drum 316a and disengage the slower gear or gearsfrom drum 316a and input shaft 26. The remainder of input gears230g-230l not coupled to a corresponding output gear 236 by connectorgear 40 are coupled to drum 316a by pawls 120 and rotate at a speedequal to the speed of drum 316a. Accordingly, uni-directional freewheeling mechanism 228 will couple the fasted gear train between drums316a and 316b acting as the input and output shafts, respectively, ofthe transmission. As a result, adjacent gear sets 38 are being rotatedat relatively the same speed when a successive adjacent connector gear40 is being moved into engagement with the successive adjacent gear set238. Thus, shifting between gear sets 238 does not require theestablishment of a neutral state, and shifting may be performed underfull power.

Drum 316b is similar to drum 316a except that drum 316b is rotatablysupported about axle 239 by bearings 286 and 289 in an oppositeorientation with respect to drum 316a and is coupled to rotating disc287 by free wheeling mechanism 285. Drum 316b supports output gears236a-236l about axle 239.

Output gears 236a-236l are substantially identical to input gears230a-230l. Output gears 236a-236l generally comprise an array ofdifferently sized toothed wheels or gears encircling drum 316b. Outputgears 236 are carried by and rotatably encircle drum 316b. Output gears236a-236f are coupled to drum 316b by uni-directional free wheelingmechanisms 228a-228f, respectively. Output gears 236g-236l are fixedlysecured to an exterior surface of drum 316b. Gears 236 have selectivelysized radii for providing a plurality of different speed ratios whengears 236 are connected to input gears 230. Output gears 236 are spacedapart from input gears 230 and are sized and positioned with respect toinput gears 230 so that output gears 236 may be connected to input gears230 by connector gears 40.

Uni-directional free wheeling mechanisms 228a-228f are substantiallyidentical to uni-directional free wheeling mechanisms 228g-228l exceptthat ratchets 118 of mechanisms 228g-228l have opposite orientationswith respect to ratchets 118 of uni-directional free wheeling mechanisms228a-228f. Uni-directional free wheeling mechanisms 228a-228f permitgears 236a-236f to freely and individually rotate about drum 316b wheneach gear 236a-236f rotates counterclockwise relative to drum 316b.Consequently, when a plurality of output gears 236a-236f areinterconnected to a plurality of input gears 236a-236f of gear sets 238at the same time, uni-directional free wheeling mechanisms 228a-228fautomatically lock the fastest gear to drum 316b and disengage theslower gear or gears from drum 316b. The remainder of output gears236a-236f not coupled to a corresponding input gear 230 by a connectorgear 40 are locked or coupled to drum 316b by pawls 120 and rotate at aspeed equal to the speed of drum 316b. Accordingly, uni-directional freewheeling mechanism 228 will couple the fasted gear train between drums316a and 316b acting as the input and output shafts, respectively, ofthe transmission. As a result, adjacent gear sets 38 rotate atrelatively the same speed when a successive adjacent connector gear 40is being moved into engagement with the successive adjacent gear set238. Thus, shifting between gear sets 238 does not require theestablishment of a neutral state, and shifting may be performed underfull power.

Free wheeling mechanism 285 comprises a conventional uni-directionalfree wheeling mechanism as is typically used in bicycles for permittingthe rider of the bicycle to cease peddling and coast. Free wheelingmechanism 285 is coupled between drum 316b and rotating disc 287. Freewheeling mechanism 285 is mounted to an end of drum 316b between drum316b and rotating disc 287. Free wheeling mechanism 285 allows rotatingdisc 287 to freely rotate with respect to drum 316b when rotating disc287 rotates in a first direction relative to the rotation of drum 316b.Free wheeling mechanism 287 couples drum 316b to rotating disc 287 asall other times so that rotation of drum 316b transmits torque torotating disc 287. As with conventional free wheeling mechanisms, freewheeling mechanism 285 permits wheel 225 to rotate at a faster speedthan the rotational speed of drum 316b. Thus, free wheeling mechanism285 permits the rider to cease peddling and coast.

Rotating disc 287 is a generally flat circular disc or plate fixedlycoupled to spokes 243 of wheel 225 and fixedly coupled to free wheelingmechanism 285 and drum 316b. Rotating disc 287 is further rotatablycoupled to fixed disc 282 by bearings 291 and rotatably supported aboutaxle 239 by bearings 289. Rotating disc 287, free wheeling mechanism 285and drum 316b form an output shaft for transmitting power fromtransmission 220 to wheel 225. Rotation of rotating disc 287 causescorresponding rotation of wheel 225. As can be appreciated, the outputshaft formed by rotating disc 287, free wheeling mechanism 285 and drum316b may have a variety of different configurations whereinuni-directional free wheeling mechanisms are disposed between the outputgears and the output shaft.

Bearing/spoke ring 288 is a generally annular ring connected betweenspokes 243 and bearing 292. Bearing/spoke ring 288 freely rotates aboutbearing 292 and supports spokes 43 and wheel 225.

As with transmission 20, transmission 220 additionally includes aplurality of connector gears 40 (shown in FIGS. 1 and 5-8) which areactuated into mutual engagement with input gears 230 and output gears236 by shifting mechanism 42 (shown in FIGS. 7-9). Shifting between gearsets to change speed ratios in transmission 220 is performed byactuating shifting mechanism 42 to selectively position connector gears40 in mutual rotary engagement with input gears 230 and output gears236. Selector cam 56 of shifter 42 is configured such that a secondconnector gear 40 is pivoted into engagement with the successive gearset 238 formed from one of input gears 230 and one of output gears 236before the proceeding connector gear 40 is biased out of engagement withthe preceding gear set 238. Uni-directional free wheeling mechanisms228a-228l permit a plurality of gear sets 238 to be interconnected atonce without transmission 220 locking up because uni-directional freewheeling mechanisms 228a-228l permit only one gear set 238 to be lockedbetween input shaft 226 and drum 316b to transfer power. As a result,power is transmitted from sprocket 229 through input shaft 226 and drum316a across one of gear sets 238 to drum 316b. Power is furthertransmitted from drum 316b to rotating disc 287 through free wheelingmechanism 285 to rotate wheel 225 about the axis of axle 239. Upon thecessation of peddling by a rider, uni-directional free wheelingmechanism 285 permits rotating disc 287 and wheel 225 to freely rotatewith respect to drum 316b and output gears 238 about the axis of axle239 for coasting. Alternatively, free wheeling mechanism 285 may beomitted, wherein drum 316b is fixedly coupled to rotating disc 287 andwherein uni-directional free wheeling mechanisms 228 provide the releasebetween wheel 225 and the pedals.

Because transmission 220 is assembled as part of wheel 225 and issupported by frame 222 by conventional wheel drop outs 235, transmission220 easily mounts to existing bicycles, reduces torque forces and allowsfor easy adjustment of the range of speed ratios. Because transmission220 is assembled as part of rear wheel 225 and is supported byconventional wheel drop outs 235, transmission 220 does not requiremodifications to conventional, pre-existing bike frames, such as bikeframe 222. Furthermore, because transmission 220 does not requiremodifications to frame 222, transmission 220 may be preassembledseparate from bicycle 221 and may be utilized in existing derailleurbicycles or other existing conventional bicycles. Preferably,transmission 220 fits within the standard width between the drop outs ofseven and eight speed rear hubs. In the preferred embodimentillustrated, transmission 220 forms hub 441 having a diameter of about12.6 inches and a total width of about 5.0 inches between the drop outs235.

In addition, locating transmission 220 at the rear wheel hub reducestorque forces. Because rear sprocket 229 and input shaft 226 are notdirectly connected to pedal cranks 210 and 211, torque from pedal cranks210 and 211 is not directly transmitted to rear sprocket 229 and inputshaft 226 of transmission 220. As a result, torque is reduced by virtueof having a larger sprocket coupled to pedal cranks 210, 211 and asmaller sprocket coupled to transmission 220. In the preferredembodiment, torque forces are reduced by approximately 47 percent ascompared to transmission 20 which is illustrated as having an inputshaft 26 coupled to left and right pedal cranks 110, 111 (see FIG. 2).

Furthermore, transmission 220 allows for easy adjustment of the range ofspeed ratios. For example, transmission 220 may be standardized toprovide a preferred speed-ratio range such as a range equivalent to an11/64 cassette (50/24 chain rings and 11/33 rear hub cassette).Transmission 220 allows the overall speed-ratio range to be adjustedupward or downward by simply using a different drive sprocket 227 or adifferent rear sprocket 229. Thus, a single transmission 220 may be usedfor a variety of road, off-road, touring, tandem, commuting andrecreational applications.

FIGS. 13 and 14 illustrate transmission 420, an alternate embodiment oftransmission 220 shown in FIGS. 10-12. FIG. 13 is a side elevationalview depicting transmission 420 as part of bicycle 421 including frame222, front wheel 223, rear wheel 425, left and right pedal cranks 210,211, drive sprocket 227, rear wheel sprocket 229 and chain 231. FIG. 14is a horizontal cross-sectional view of transmission 420. Bicycle 421 issimilar to bicycle 221 except that bicycle 421 includes transmission420. For ease of illustration, those elements of bicycle 421 which arethe same as bicycle 221 are numbered similarly.

As best shown by FIG. 14, transmission 420 is assembled as part of hub441 of wheel 425. Transmission 420 is identical to transmission 220except that transmission 420 includes fixed disc 482, fixed plates 483and 484, and rotating disc 487 in lieu of fixed disc 282, rotating disc287 and bearing/spoke ring 288. For ease of illustration, those otherelements of transmission 420 which are similar to corresponding elementsof transmission 220 are numbered similarly.

Fixed disc 482 is similar to fixed disc 282. Fixed plate 483 is agenerally flat plate fixedly connected to fixed disc 482 and isconnected by yoke pivot rods 486 to opposing fixed plate 484. Fixedplates 483 and 484 rotatably support input gears 230, output gears 236,as well as the connector gears and yokes (not shown).

Rotating disc 487 is round and has a generally C-shaped cross-section.Disc 487 is sized for housing and enclosing input gears 230, outputgears 236 as well as connector gears 40 (shown in FIGS. 1 and 5-8) andshifting mechanism 42 (shown in FIGS. 1 and 7-9). Rotating disc 487 isfixedly coupled to spokes 243 and rim 245. Rotating disc 487 isrotatably coupled with respect to fixed disc 482 by bearings 291 and isrotatably supported about axle 239 by bearings 286 and 289.

Transmission 420 functions nearly identical to transmission 220. Poweris transmitted from input shaft 226 and drum 316a to drum 316b by inputgears 230, connector gears 40 and output gears 236. Power is transmittedfrom drum 316b across free wheeling mechanism 285 to rotating disc 487which is fixedly coupled to wheel 225 to rotate wheel 425 about axle239. Uni-directional free wheeling mechanisms 228a-228l permit shiftingunder continuous power. In addition, transmission 420 assembled as partof wheel 425 may be easily mounted in preexisting conventional bicycleframes.

Conclusion

The present invention provides an enclosed, linearly sequenced gearedtransmission that shifts under continuous power, has a minimum number ofgears engaged at any one time to minimize friction and power loss, anddoes not require continuous adjustment. The present invention alsoprovides tailored speed ratios and progressive power curves fordifferent uses.

As mentioned earlier, the present invention may be used in a variety ofvehicles and stationary equipment. For example, when employed in winchesand block/tackle equipment where a high-speed gear is used to take upslack and a low-speed gear is used under full load, the presentinvention may be employed to automatically shift between the two gearapplications by using the cable or rope tension to engage a connectorgear for the lower speed. As a result, when the cable or rope tension isslack, the yoke spring disengages the low gear to cause slack to betaken up at a higher speed.

Although the present invention has been described with reference topreferred embodiments, workers skilled in the art will recognize thatchanges may be made in form and detail without departing from the spiritand scope of the invention.

What is claimed is:
 1. A multi-speed transmission for transmitting powerbetween a first shaft and second shaft, the transmission comprising:aplurality of gear sets, each gear set including:a first gear encirclingthe first shaft; a uni-directional free wheeling mechanism between thefirst gear and the first shaft, wherein the uni-directional freewheeling mechanism permits the first gear to freely rotate about theshaft when the first gear rotates in a preselected direction relative tothe rotation of the first shaft and couples the first gear to the firstshaft at all other times; and a second gear coupled to the second shaft;and means for interconnecting the first gear and the second gear so thatforce is transferred between the first gear and the second gear, whereinat least two of the gear sets are simultaneously interconnected duringshifting.
 2. The multi-speed transmission of claim 1 wherein the meansfor interconnecting includes:a plurality of connector gearscorresponding to the plurality of gear sets, each connector gear beingmovable between an engaged position and a disengaged position, whereineach connector gear mutually engages the first gear and the second gearin the engaged position and is disengaged from the first gear and thesecond gear in the disengaged position; and a shifting mechanism formoving each one of the plurality of connector gears between the engagedposition and the disengaged position.
 3. The transmission of claim 2wherein the shifting mechanism includes:a plurality of yokescorresponding to the plurality of connector gears, each yoke having afirst end rotatably coupled to a corresponding connector gear and asecond end mounted about a pivot so that the corresponding connectorgear can be moved into mutual engagement with the first and secondgears; and means for moving each one of the plurality of yokes about thepivot.
 4. The transmission of claim 1 wherein the uni-directional freewheeling mechanism permits the first gear to freely rotate about thefirst shaft when the first gear rotates at a speed less than the speedat which the first shaft rotates and wherein the uni-directional freewheeling mechanism couples the first gear to the first shaft at allother times.
 5. The transmission of claim 1 wherein the uni-directionalfree wheeling mechanism includes:a drum having an outer surface andbeing coupled to the first shaft between the first shaft and the firstgear, the outer surface of the drum defining a slot; a plurality ofteeth on an inner diameter of the first gear and encircling the outersurface of the drum, the teeth being oriented in a first direction; anda pawl positioned within the slot of the drum and biased for engagingthe teeth of the first gear so that the pawl permits the first gear tofreely rotate about the first shaft when the first gear rotates in thepreselected direction relative to the rotation of the first shaft and sothat the pawl locks the first gear to the drum at all other times. 6.The transmission of claim 1 including:a housing enclosing the pluralityof gear sets and the plurality of connector gears to protect theplurality of gear sets and the plurality of connector gears.
 7. Amulti-speed transmission for transmitting power between a first shaftand a second shaft, the transmission comprising:a plurality of gearsets, each gear set including:a first gear encircling the first shaft; auni-directional free wheeling mechanism between the first gear and thefirst shaft, wherein the uni-directional free wheeling mechanism permitsthe first gear to freely rotate about the shaft when the first gearrotates in a preselected direction relative to the rotation of the firstshaft and couples the first gear to the first shaft at all other times;and a second gear coupled to the second shaft; and means forinterconnecting the first gear and the second gear so that force istransferred between the first gear and the second gear, wherein themeans for interconnecting includes:a plurality of connector gearscorresponding to the plurality of gear sets, each connector gear beingmovable between an engaged position and a disengaged position, whereineach connector gear mutually engages the first gear and the second gearin the engaged position and is disengaged from the first gear and thesecond gear in the disengaged position; and a shifting mechanism formoving each one of the plurality of connector gears between the engagedposition and the disengaged position, wherein the shifting mechanismincludes:a plurality of yokes corresponding to the plurality ofconnector gears, each yoke having a first end rotatable coupled to acorresponding connector gear and a second end mounted about a pivot sothat the corresponding connector gear can be moved into mutualengagement with the first and second gears; and means for moving eachone of the plurality of yokes about the pivot, wherein the means formoving includes:a cam shaft having a plurality of axially and radiallyspaced lobes, each lobe having a first surface for engaging one of theplurality of yokes so that the corresponding connector gear is pivotedinto mutual engagement with the first and second gears of itscorresponding gear set and a second surface for engagement with one ofthe plurality of yokes so that the same corresponding connector gear ispivoted out of mutual engagement with the first and second gears of itscorresponding gear set; and means for rotating the cam shaft.
 8. Thetransmission of claim 7 wherein the means for rotating the cam shaftincludes:a cam disk coupled to the cam shaft; and a cable engaging thecam disk, wherein movement of the cable rotates the cam disk.
 9. Thetransmission of claim 8 further including:an index to indicate cam diskpositions for different gear speeds and to maintain the cam disk in aselected position.
 10. A multi-speed transmission for transmitting powerbetween an input shaft and an output shaft, the transmissioncomprising:a first array of gears of decreasing size disposed about theinput shaft; a second opposing array of gears of increasing sizedisposed about the output shaft opposite the first array ofgears,wherein each gear of the output shaft corresponds to a gear of theinput shaft and wherein each corresponding pair of gears includes auni-directional free wheeling mechanism between at least one of thegears and its respective shaft so that the gear freely rotates about itsshaft when the gear rotates in a preselected direction relative to therotation of its shaft and so that the gear is coupled to its shaft atall other times; an array of connector gears, each connector gearcorresponding to each corresponding pair of gears of the input andoutput shafts and being movable into mutual engagement with thecorresponding pair of gears of the input and output shafts; and ashifting mechanism for moving each one of the array of connector gearsinto and out of engagement with a corresponding pair of gears of theinput and output shafts; wherein at least one of the array of connectorgears is maintained in engagement with a corresponding pair of gears ofthe input and output shafts, and wherein at least two correspondingpairs of gears are simultaneously engaged during shifting.
 11. Animproved multi-speed transmission for transmitting power between aninput shaft and an output shaft, the input shaft carrying differentlysized gears and the output shaft carrying differently sized gears,wherein the output shaft is rotated at a variety of speeds byinterconnecting the differently sized gears of the input shaft and theoutput shaft, an improvement comprising:a uni-directional free wheelingmechanism between at least one of the differently sized gears of atleast one of the input and output shafts and the shaft carrying thegear, wherein the uni-directional free wheeling mechanism permits thegear to freely rotate about the shaft when the gear rotates in apreselected direction relative to the rotation of the shaft and whereinthe uni-directional free wheeling mechanism automatically couples thegear to the shaft at all other times and wherein at least two of thedifferently sized gears of the input shaft and at least two of thedifferently sized gears of the output shaft are simultaneouslyinterconnected during shifting.
 12. A multi-speed transmission fortransmitting power between an input shaft and an output shaft, thetransmission comprising:a first array of input gears fixedly coupled tothe input shaft; a second array of input gears encircling the inputshaft; a first plurality of uni-directional free wheeling mechanismscorresponding to each one of the second array of input gears between theinput shaft and each one of the second array of input gears, eachuni-directional free wheeling mechanism permitting the correspondinggear to freely rotate about the input shaft when the corresponding gearrotates in a preselected direction relative to the rotation of the inputshaft, each uni-directional free wheeling mechanism further coupling thecorresponding gear to the input shaft at all other times; a first arrayof output gears fixedly coupled to the output shaft, each one of thefirst array of output gears corresponding to one of the second array ofinput gears; a second array of output gears encircling the output shaft,each one of the second array of output gears corresponding to one of thefirst array of input gears; a second plurality of uni-directional freewheeling mechanisms corresponding to each one of the second array ofoutput gears between the output shaft and each one of the second arrayof output gears, each uni-directional free wheeling mechanism permittingthe corresponding gear to freely rotate about the output shaft when thecorresponding gear rotates in a preselected direction relative to therotation of the output shaft, each uni-directional free wheelingmechanism further coupling the corresponding gear to the output shaft atall other times; and means for selectively interconnecting at least oneof the gears of the input shaft to at least one of the gears of theoutput shaft to transmit power from the input shaft to the output shaftwherein at least two of the input gears and at least two of the outputgears are simultaneously interconnected during shifting.
 13. A cycletransmission for transmitting power between a drive sprocket and a cyclewheel having a hub, the transmission comprising:an input shaft mountedwithin the hub; a rotating member coupled to the wheel, wherein rotationof the rotating member rotates the wheel; means for transferring powerfrom the drive sprocket to the input shaft; a first plurality of gearscarried by the input shaft; a second plurality of gears carried by therotating member; means for interconnecting gears of the first pluralityof gears to gears of the second plurality of gears to transmit powerfrom the input shaft to the rotating member, wherein at least two of thegears of the first plurality of gears and at least two of the gears ofthe second plurality of gears are simultaneously interconnected duringshifting; and a first uni-directional free wheeling mechanism betweenone of the gears of the first plurality of gears or the second pluralityof gears and the shaft or member carrying the gear, wherein theuni-directional free wheeling mechanism permits the gear to freelyrotate about the shaft or member when the gear rotates in a preselecteddirection relative to the rotation of the shaft or member and whereinthe uni-directional free wheeling mechanism automatically couples thegear to the shaft or member at all other times.
 14. The transmission ofclaim 13 wherein the wheel includes a fixed axle and wherein the hubincludes:a support member rotatably supported about the axle andsupporting the second plurality of gears; and a second uni-directionalfree wheeling mechanism between the support member and the secondplurality of gears for permitting the support member to rotate freelyabout the axle when the gear rotates in the preselected directionrelative to the rotation of the axle and wherein the uni-directionalfree wheeling mechanism automatically couples the gear to the supportmember at all other times.
 15. The transmission of claim 13 wherein thetransmission includes a fixed axle and wherein the hub furtherincludes:a first side fixedly coupled to the axle for alignment of thetransmission; and a second side rotatably supported about the axle andcoupled between the output shaft and the wheel to transmit torque to thewheel.
 16. A multi-speed transmission for transmitting power between afirst shaft and a second shaft, the transmission comprising:a pluralityof first torque transmitting members coupled to the first shaft; aplurality of second torque transmitting members coupled to the secondshaft; a uni-directional free wheeling mechanism between a first memberand the first shaft, wherein the uni-directional free wheeling mechanismpermits the first member to freely rotate about the first shaft when thefirst member rotates in a preselected direction relative to the rotationof the first shaft and locks the first member to the first shaft at allother times; and means for selectively and simultaneouslyinterconnecting respective first and second members to interconnect thefirst shaft with the second shaft, wherein at least two first membersand at least two second members are simultaneously interconnected duringshifting.